Lubricating oils for present day internal combustion engines contain a multitude of additives functioning as detergent dispersants, viscosity index improvers, oxidation inhibitors, pour depressors, oiliness agents, etc.,in order to meet the demands placed thereon. A widely used class of additives are the polymers of one or more alkyl acrylate or methacrylate and a dialkylaminoalkyl methacrylate such as tetrapolymer of butyl methacrylate, lauryl methacrylate, stearyl methacrylate and dimethylaminoethyl methacrylate. These amino containing methacrylates have the multiple properties of VI improving, pour depressing and detergent-dispersancy. Although the amino polymethacrylates are effective viscosity index improvers, pour depressors and/or detergent-dispersants, they are believed to be the source of a problem occurring with increasing frequency, in the modern high temperature internal combustion engines employing heavy duty multi-viscosity type lubricating oils, e.g., SAE 1OW-40 grades. Specifically, the heavy duty motor oils containing the amino polymethacrylates in the high temperature engines after several thousand miles of usage undesirably substantially increase in apparent viscosity and in some instances the entire lubricating oil composition forms a gel. Investigation indicates that at high temperatures the engine "blow-by" appears to cause polymerization of the additives in these heavy duty oils. Engine "blow-by" is a mixture of the fuel vapors and combustion products of the cylinder which was blown past or "blow-by" the piston rings into the crankcase. In the absence of detergent-dispersant additives the "blow-by" coagulates causing sludge deposits.